Polyamide resins are widely used as engineering plastics having excellent mechanical strength such as impact resistance and friction/abrasion resistance as well as excellent heat resistance and oil resistance in the fields of automotive parts, electronic/electric equipment parts, office automation equipment parts, machine parts, construction materials/housing parts and the like, and recently have found increasingly wide applications.
Known polyamide resins include polyamide 6, polyamide 66, polyamide 610 and the like. Generally, polyamide resins had the disadvantage that their mechanical properties such as flexural rigidity and elastic modulus decrease when they absorb water, and more specifically, polyamide resins such as polyamide 6, polyamide 66 and polyamide 610 had the disadvantage that their elastic modulus decreases as they absorb water, which results in their limited field of application and low reliability for long-term use.
Further, m-xylylene adipamide (hereinafter sometimes referred to as “MXD6”) derived from m-xylylenediamine and adipic acid is also known and positioned as a very excellent polyamide resin because it contains an aromatic ring in the main chain unlike the polyamide resins described above so that it has high rigidity and it is also suitable for precision molding, and therefore, MXD6 has recently been more widely used as a molding material, especially as an injection molding material in various fields including parts of vehicles such as automobiles, general machine parts, precision machine parts, electronic/electric equipment parts, leisure/sports goods, civil engineering and construction materials, etc.
However, MXD6 also suffers from a decrease in elastic modulus due to wetting, which results in its limited field of application but to a lesser extent than polyamide 6, polyamide 66 and polyamide 610.
Lighter and stronger polyamide resin materials are also needed and a known xylylene polyamide resin lighter than MXD6 includes a xylylene sebacamide-based polyamide resin derived from xylylenediamine and sebacic acid (hereinafter sometimes referred to as “XD10”) (see patent document 1), which has been highly expected as a high-performance polyamide resin. However, this XD10 may also cause the problems due to wetting as described above.